US7641677B2 - Compression bone fragment wire - Google Patents

Abstract

A bone fragment wire connects a bone fragment to an anchor bone for a healing duration. The bone fragment wire has a distal bone penetration section which is advanced into the bone and a proximal bone exterior section. The proximal bone exterior section is longer than the bone penetration section, and thus extends substantially out of the bone during healing of the bone. The bone penetration section includes a distal bone anchor section which threadingly engages the anchor bone, and a proximal fragment section of small diameter. The fragment section fits within the overbore created by advancing the bone anchor section through the bone fragment, and thus extends through but does not positively engage the bone fragment. A compression engagement on a distal end of the bone exterior section provides a compression shoulder. In one embodiment the compression engagement is provided by a threaded compression nut, while in another embodiment the compression engagement is permanently affixed to the bone wire. The shoulder makes substantial contact with an exterior surface of the bone fragment, biasing the bone fragment toward the anchor bone with a controlled compression force. The compression engagement is further adapted, such as through thread form and/or with a sloped proximal side, to enable the bone wire to be more easily removed from the healed fracture without damaging surrounding tissue.

Description

CROSS-REFERENCE TO RELATED APPLICATION(S)

None.

BACKGROUND OF THE INVENTION

The present application is directed to bone pins and wires, and, more specifically, to bone pins and wires used to attach a bone fragment to an anchor bone for a healing duration.

Bone pins and wires are characterized by having a relatively small diameter, such as a diameter less than 0.1 inch (2.5 mm). Bone pins which are elongated wires are commonly referred to as “Kirschner wires” or “K-wires”. An example of this is disclosed in U.S. Pat. No. 2,393,694 to Kirschner. The term “bone pin” is more commonly used for shorter structures, such as a length of 2 inches or less, while the term “K-wire” more commonly applies to longer structures, such as a length up to 12 inches, but there is no bright line definition clearly distinguishing between a “bone pin” and a “K-wire” based on length. The present application uses the term “bone wire” to refer to such a small diameter structure and including either a bone pin or a K-wire, regardless of length, but excluding, for instance, a larger diameter bone screw.

Such bone wires have long been used in the orthopaedic arts for several different purposes. Bone wires are often used during surgery as a temporary guide in targeting and directing another more permanent device, such as a cannulated bone screw running over the bone wire, into a bone fragment or anchor bone. Bone wires have been implanted to anchor other devices, such as a bone plate, fixator or external splint device, to a fractured bone. Bone wires have also been used to secure many types of bone fragments to anchor bones, where the term bone “fragment” refers to any part of bone separated by a fracture, regardless of whether that fracture is partial or completely through the bone.

Bone wires commonly have a pointed tip, which may be further fabricated with a drill type structure such that rotation of the bone wire about its longitudinal axis helps to remove bone material from the hole into which the bone wire is advanced. The bone wires may or may not have fine threads to further assist in axially advancing the bone wire into its hole during rotation. While bone wires have been used for fragment fixation, design improvements are needed to have a small diameter bone wire structure which more easily places an appropriate compression force on the interface between the bone fragment and its anchor bone.

BRIEF SUMMARY OF THE INVENTION

The present invention is a bone fragment wire for connecting a bone fragment to an anchor bone for a healing duration. The bone fragment wire has a bone penetration section which is advanced into the bone. The bone fragment wire has a bone exterior section which extends substantially out of the bone during healing of the bone. The bone penetration section includes a distal bone anchor section which threadingly engages the anchor bone, and a fragment section which extends through but does not positively engage the bone fragment. The fragment section thus fits within the overbore created by advancing the bone anchor section through the bone fragment. A compression engagement on a distal end of the bone exterior section provides a compression shoulder. The shoulder makes substantial contact with an exterior surface of the bone fragment, biasing the bone fragment toward the anchor bone with a controlled compression force.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a first embodiment of the invention.

FIG. 2 is a cross sectional view of the threads/nuts taken at area2 ofFIG. 1.

FIG. 3 is a cross sectional view of the threads taken atarea3 ofFIG. 1.

FIG. 4 is a side view of the second embodiment of the invention.

FIG. 5 is a side view of the second embodiment of the invention during implantation with a fractured bone.

FIG. 6 is a side view of the second embodiment of the invention after implantation.

While the above-identified drawing figures set forth preferred embodiments, other embodiments of the present invention are also contemplated, some of which are noted in the discussion. In all cases, this disclosure presents the illustrated embodiments of the present invention by way of representation and not limitation. Numerous other minor modifications and embodiments can be devised by those skilled in the art which fall within the scope and spirit of the principles of this invention.

DETAILED DESCRIPTION

A preferredfragment bone wire10 of the present invention includes ananchor section12 located distally of anintermediate fragment section14. Acompression section16 is provided proximally of theintermediate fragment section14, and arotation section18 is provided proximally of thecompression section16. In the surgical method of using thebone wire10, theanchor section12 and thefragment section14 penetrate thebone20, while thecompression section16 and therotation section18 remain outside on the exterior of thebone20. Thebone penetrating section22, i.e., theanchor section12 and thefragment section14, are shorter in combined length than the combined length of thebone exterior section24, i.e., thecompression section16 and therotation section18.

Thedistal anchor section12 has ashaft portion26 terminating in adrill tip28. The hole which is made in thefragment30 and theanchor bone32 for thebone wire10 is generally not pre-drilled, but rather is drilled by thedrill tip28 during advancement of thebone wire10 through thefragment30 and into theanchor bone32. Thedrill tip28 may be constructed in accordance with drill tip techniques used on current bone wires, such as a three-sided sharp trocar. As known in the art, thisdrill tip28 assists thebone wire10 in drilling a hole throughbone20, breaking upbone20 and removing bone powder and minute bone pieces from the hole during drilling.

Theshaft portion26 includesanchor threads34, which serve both to advance thebone wire10 into theanchor bone32 during rotation, and to anchor thebone wire10 into theanchor bone32 after implantation is completed. Theshaft portion26 has a relatively short length suitable for anchoring in a desiredanchor bone32. Theshaft portion26 of thedistal anchor section12 may have a length of 5 mm for about a five millimeter anchor. During use, thebone wire10 is advanced through afragment30 and into ananchor bone32 until thedistal anchor section12 is substantially entirely within theanchor bone32. Theanchor threads34 are constructed with an appropriate width and pitch to suitably perform the advancing and anchoring functions in abone wire10 with its small diameter. For instance, theanchor threads34 in a preferred “thin” embodiment have a minor diameter of 1.65 mm and a major diameter of 2 mm. In a preferred “thick” embodiment, theanchor threads34 have a minor diameter of 2 mm and a major diameter of 2.35 mm. Theanchor threads34 in a preferred embodiment have a pitch of 0.5 mm per rotation.

Since thefragment30 and theanchor bone32 are not typically predrilled, the hole for thebone wire10 in thefragment30 andanchor bone32 is not typically pre-tapped. Thus, theanchor threads34 are preferably self-tapping on the distal side of theanchor section12, as commonly known in the screw thread art. Having theanchor threads34 be self-tapping for insertion decreases the number of surgical steps and surgery time as compared to tapping with a separate tap, while providing a firmer attachment with less bone damage and requiring less drill force as compared to not tapping at all.

Thebone wire10 of the present invention is intended to be surgically implanted and left within the patient for a healing duration while thefragment30 attaches and grows together to theanchor bone32. During this bone growth healing duration, bone tissue may grow back within the threads cut into thefragment30 by theanchor threads34. To assist in removing theanchor section12 through thefragment30 after the healing duration, thepreferred threads34 are self-tapping on the proximal side as well. Having thethreads34 be self-tapping on the proximal side reduces the torque necessary for removal, decreasing the likelihood of shearing breakage of thebone wire10 during removal and decreasing the likelihood of damage to the surrounding bone and surrounding tissue during removal.

As shown inFIG. 2, thepreferred anchor threads34 have a thread form which is angled against pull-out. The angle of the thread form can significantly increase the pull-out force which can be supported by thebone wire10, which can be very important especially if theanchor bone32 is weak, damaged or overly pourous.

Thefragment section14 has a diameter which is smaller than at least the major diameter of theanchor section12, and preferably smaller than the minor diameter of theanchor section12 as well. Being smaller in diameter, thefragment section14 does not interfere with the hole in thefragment30 created by theanchor section12 when theanchor section12 was advanced through thefragment30. For instance, thefragment section14 may have a smooth cylindrical profile, contrasted against the threadedanchor section12. In the preferred “thin” embodiments, thefragment section14 has a smooth cylindrical profile with a diameter of 1.5 mm. Thefragment section14 thus follows behind the minor diameter on the threadedanchor section12 of 1.65 mm and does not substantially engage the bone of thefragment30. In the preferred “thick” embodiment, thefragment section14 has a smooth cylindrical profile with a diameter of 1.85 mm. Thefragment section14 thus follows behind the minor diameter on the threadedanchor section12 of 2 mm and does not substantially engage the bone of thefragment30. With the small diameter of thefragment section14, thebone wire10 of the present invention can be thought of as having a reverse taper, with theproximal fragment section14 of thewire10 being narrower in diameter than thedistal anchor section12.

The length of thefragment section14 should approximately correspond with the length of thefragment30 in the injuredbone20. Obviously, the length of thefragment30 depends upon the injury, and is not the same for all fractured bones. Particularly for “thin” embodiments, thebone wire10 may be provided as part of a kit which allows the surgeon to select the length of thefragment section14 as desired for aparticular fragment30. For instance, the kit may includebone wires10 with fragment section lengths that vary in 2 mm increments, i.e., lengths for thefragment section14 of 2, 4, 6, 8, 10, 12, 14 and 16 mm.

Thecompression section16 provides acompression engagement36 which defines the proximal extent of thefragment section14. The purpose of thecompression engagement36 is to place a compression force on an exterior surface of thebone fragment30, and thus externally bias thebone fragment30 toward theanchor bone32. Thecompression engagement36 includes ashoulder surface38 extending at a substantial angle to the wire axis for substantial contact with an exterior surface of thebone fragment30. Thebone wire10 thus allows for compression via thecompression engagement36 after insertion through the skin and placement of thecompression engagement36 against thebone fragment30.

In the embodiment ofFIGS. 1-3, thecompression engagement36 is provided by one ormore nuts40,42 placed on a proximal threadedshaft section44. A preferred length for the proximal threadedshaft section44 is 15 mm. Thepreferred compression nut40 has a compression shoulder section46 and adrive section48. The compression shoulder section46 is on the distal side of thenut40 and has a cylindrical outer profile, such as an outer diameter of 4 mm. The compression shoulder section46 has an inside bore, which is large enough to fit over both the proximal threadedshaft section44 and thefragment section14. For instance, the inside bore may be a smooth cylindrical hole with a 1.85 mm diameter. The length of the compression shoulder section46 may be designed as desired to correspond with the amount of adjustment and flexibility desired. If kits ofbone wires10 are provided with a 2 mm variance in length offragment sections14, then the length of the compression shoulder section46 may match this variance, i.e., extend axially for at least 2 mm.

Thedrive section48 is on the proximal side of thenut40 to enable the surgeon to rotationally advance thecompression nut40 with a standard tool. For instance, thedrive section48 of thecompression nut40 may have a traditional hexagonal profile with a distance between opposing flats of about 3.45 mm. Thedrive section48 is internally threaded to mate with the external threads of the proximal threadedshaft section44, such as a threaded length of 4 mm. If desired, alock nut42 may be further used to secure thecompression nut40 at a desired axial position, such as alock nut42 of 2 mm.

In the embodiment ofFIGS. 4-6, thecompression engagement36 is a tear-drop shoulder50. In contrast with thecompression nut40, the tear-drop shoulder50 is integrally formed or permanently affixed to the rest of thebone wire10.

With either thecompression nut40 or the tear-drop shoulder50, adistal shoulder surface38 is provided for contact with the exterior surface of thebone fragment30. Thedistal shoulder surface38 preferably has a curvature of large radius, for enhancing the likelihood of a smooth engagement with the exterior surface of thefragment30. If desired, thebone wire10 may be included as part of a kit with severaldifferent compression engagements36 each having a different radius of curvature on thedistal shoulder surface38, enabling the surgeon to pick thecompression engagement36 having adistal shoulder surface38 which best matches the surface of thebone fragment30. The intent is to support the compression force with a broad surface to surface contact between thecompression engagement36 and thebone fragment30 rather than at a point contact which could dig into and damage thebone fragment30.

Because thefragment section14 has too small a diameter to positively engage thefragment30, thecompression shoulder38 provides substantially all of the force pressing thebone fragment30 into theanchor bone32 during the healing duration. The present invention permits control of this compression force in either of two ways. First, the compression force can be selected by the surgeon by determining how far to rotationally advance thebone wire10 into theanchor bone32, while thecompression shoulder38 remains at a constant longitudinal position relative to thebone wire10. In the embodiment ofFIGS. 1-3 and depending upon the relative frictional forces involved, supplying a compression force in this manner may require the surgeon to positively rotate thecompression nut40 during rotation of thebone wire10. In the embodiment ofFIGS. 4-6, the tear-drop shoulder50 is integrally formed or permanently secured to thebone wire10, so the surgeon need not take any further steps other than rotating thebone wire10, and thecompression shoulder38 will always advance with therotating bone wire10.

Second, in the embodiment ofFIGS. 1-3, the compression force can be selected by the surgeon after thebone wire10 is fully advanced into theanchor bone32, by rotationally advancing thecompression nut40 relative to astationary bone wire10. This allows the surgeon to customize thebone wire10 as to the length between thetip28 of thebone wire10 and thecompression shoulder38. Depending upon the relative frictional forces involved, supplying a compression force in this manner may require the surgeon to positively hold thebone wire10 in a non-rotating position during rotation of thecompression nut40.

With either embodiment, the surgeon can monitor the amount of compression force being applied in any of several different ways. First, the surgeon may be able to visually (either directly or with the aid of scoping equipment) see advancement of thefragment30 toward theanchor bone32. Note, for instance, thatFIG. 5 shows thefragment30 separated from theanchor bone32 by aslight gap52, andFIG. 6 shows thefragment30 having been moved against theanchor bone32 to completely close thegap52. Second, the surgeon may have the sensitivity to feel the change in torque associated with advancing thecompression shoulder38 against thefragment30, either by hand or with the aid of a monitoring tool such as a torque wrench. Such “feel” of the advancing torque requirements is relatively easy with the embodiment ofFIGS. 1-3 if thebone wire10 is stationary; otherwise, the surgeon must be careful to distinguish between any change in torque required to rotationally advance thebone wire10 as distinguished from any change in torque required to rotationally advance thecompression shoulder38. Third, the amount of torque applied in advancing thecompression shoulder38 can be controlled below a maximum threshold value. Either a drill having a controlled or set maximum torque can be used, or the rotational engagement structure (for instance, the flats of the compression nut40) can be designed to shear off at a desired torque. In practice, all three methods may be used simultaneously.

The embodiment ofFIGS. 1-3 can provide a further benefit, provided that a proximal threadedshaft section44 which supports thenut40 is made long enough and of small enough diameter. Namely, the proximal threadedshaft section44 can be substantially longer than the desired amount of compression movement. Provided the proximal threadedshaft section44 will fit within the overbore of thefragment30 created by theanchor section12, thebone wire10 may be advanced until a substantial portion of the proximal threadedshaft section44 resides within thefragment30. The selectable length of thefragment section14 is then not as critical. For instance, a preferred length for the proximal threadedshaft section44 in the embodiment ofFIGS. 1-3 is 15 mm, while thepreferred compression nut40 together with thelock nut42 have an axial length of only 8 mm. Provided the diameter of the proximal threadedshaft section44 permits it to fit within the overbore drilled by theanchor section12, then up to 7 mm of the proximal threadedshaft section44 can be placed within the overbore in thefragment30. Thecompression nut40 can be advanced until at least the compression shoulder section46 extends over thefragment section14, i.e., axially for 2 mm beyond the end of the proximal threadedshaft section44, for a total range of compression motion for thecompression shoulder38 of 9 mm. With this large range of compression motion for thecompression shoulder38, the kit need only includefragment sections14 with a length variance of the total range of compression motion, e.g, a kit withfragment sections14 of 2, 11 and 20 mm would allow use on afragment30 of anywhere from 0 to 27 mm in thickness. If the length of the proximal threadedshaft section44 was lengthened to 33 mm, then asingle bone wire10 with afragment section14 of 2 mm could be used onfragments30 of 0 to 27 mm in thickness.

However, the tradeoff for this flexibility in length lies in the strength of thebone wire10. In particular, if thefragment section14 has a diameter of 1.5 mm, then the major diameter of the proximal threadedshaft section44 should be 1.5 mm or less to fit within the overbore in thefragment30 to the same extent as thefragment section14 fits within the overbore. If the thread depth is retained at at least 0.15 mm, and major diameter of 1.5 mm results in a minor diameter of no greater than 1.2 mm. However, the minor diameter must be strong enough to support the required torque to drive theanchor section12 through thefragment30 and through theanchor bone32. With current materials, a minor diameter of 1.2 mm over a 33 mm length results in a brittle, weak product, which is likely to break off during driving through thebone20 or during use.

Instead, the preferred embodiments of thebone wire10 retain a minimum diameter of at least 1.5 mm throughout. The major diameter of the proximal threadedshaft section44 is accordingly selected at 1.83 mm. This major diameter interferes with the minor diameter of 1.65 mm drilled by the “thin”anchor section12, and hence thebone wire10 should be used without advancing any part of the proximal threadedshaft section44 into the fragment bore. Given that no part of the proximal threadedshaft section44 extends into the fragment bore, thecompression nut40 only has 2 mm of axial advancement flexibility, and thebone wires10 are thus provided in kits of 2 mm variance in length offragment sections14. The major diameter for the proximal threadedshaft section44 of 1.83 mm does not interfere with the minor diameter of 1.85 mm drilled by the “thick”anchor section12. As such, the proximal threadedshaft section44 can extend into the fragment bore drilled by the “thick”anchor section12, and thecompression nut40 in the preferred “thick” embodiment has a full 9 mm of axial advancement flexibility.

Therotation section18 of thebone wire10 extends substantially beyond the end of thecompression section16. In most uses, therotation section18 will extend outside the patient's skin during the entire healing duration, which can greatly facilitate healing. Therotation section18 allows thebone wire10 to be rotated without interference with tissue adjacent thebone20, so the surrounding tissue is less damaged during surgery than occurred with prior art methods. Therotation section18 allows thebone wire10 to be used in fixating the fracture with a fixator support structure as described in U.S. Pat. Nos. 6,058,748, 6,283,946, and U.S. patent application Ser. No. 10/160,470, incorporated by reference, which can allow the proper amount of stress to be placed on thebone20 during healing, substantially benefitting the healing process. The fixator support structure attaches to therotation section18 of thebone wire10. The placement of thecompression shoulder38 against thefragment30 also increases the fixation by reducing wire toggle, such as may occur during wrist motion. In the preferred embodiment, therotation section18 is cylindrical with a diameter of 1.5 mm, and extends for 100 to 150 mm.

The present invention includes several features which are specifically directed to removal of thebone wire10 after the healing duration. In contrast to most bone pins and bone screws, thebone wire10 of the present invention leaves a significant length exposed through the skin to grasp for removal without damaging tissue. In the embodiment ofFIGS. 1-3, the threads of the proximal threadedshaft section44 have a different pitch and a different shape than theanchor threads34. For instance, the proximal threadedshaft section44 may have a pitch of 0.4 mm per revolution, as compared to the preferred anchor thread pitch of 0.5 mm. Counterclockwise rotation of thebone wire10 will cause thebone wire10 to retract its anchor thread pitch, i.e., 0.5 mm per revolution. Because the proximal threadedshaft section44 has a shallower pitch than theanchor threads34, the nut(s)40,42 must retract with counterclockwise rotation of thebone wire10. That is, the nut(s)40,42 could rotate with therotating bone wire10, in which case the nut(s)40,42 would retract at the anchor thread pitch, i.e., 0.5 mm per revolution. Alternatively, even if the surrounding tissue has grown around the nut(s)40,42 and prevents rotation of the nut(s)40,42, the nut(s)40,42 will still back out at the difference between pitches, i.e., 0.1 mm per revolution of thebone wire10. Further, if thecompression nut40 rotates all of the way to the distal end of the proximal threadedshaft section44, the compression nut screw thread has a smaller inside diameter than the outside diameter of thefragment section14, preventing thecompression nut40 from further advancing onto thefragment section14.

As shown inFIG. 3, the proximal threadedshaft section44 may have a thread form which is balanced in both proximal and distal directions, in contrast to thepreferred anchor threads34 which have a thread form which is angled against pull-out. Alternatively, the thread form for the proximal threadedshaft section44 may be angled oppositely to the thread form of thepreferred anchor threads34, to better support the compression force placed on thecompression nut40.

In the embodiment ofFIGS. 4-6, theproximal surface54 of the tear-drop shoulder50 assists in removal of thebone wire10 through tissue which may grow around thebone exterior section24 of thebone wire10 during the healing duration. In particular, theproximal surface54 of the tear-drop shape is sloped for removal, with the slope angle being shallow near the axis of thebone wire10, becoming steeper at intermediate diameters, and then again becoming shallow near the maximum diameter of the tear-drop shoulder50. This shape helps to separate the overlying tissue with minimal damage to such surrounding tissue when thebone wire10 is removed. In the embodiment ofFIGS. 1-3, the proximal surface of thecompression nut40 and/or thelock nut42 could alternatively be modified to provide a similar slope for assisting in separating overlying tissue during removal.

Because of the various features of thebone wire10 of the present invention which facilitate removal, removal of thebone wire10 can be accomplished without requiring a separate incision to be made after the healing duration. Avoiding this additional incision greatly helps in healing the tissue over the fracturedbone20, both in terms of the length of time required for full healing and in terms of avoiding the build-up of scar tissue.

Thebone wire10 may be formed out of any surgically acceptable strong material, such as surgical acceptable stainless steel (such as 316 LVM, per ASTM F1350, electropolished and passivated) or a titanium alloy (such as TI-6AL-4V, per ASTM F136).

The method of use of thebone wire10 of the present invention should be readily apparent in the preceding discussion, and will be further outlined here. Insertion of thebone wire10 is performed through a small incision with blunt dissection carried to thebone20. For insertion, thebone wire10 is drilled through thefragment30, and the thickerdiameter anchor threads34 overbore a hole through thefragment30. The thickerdiameter anchor threads34 then reach theanchor bone32 and pull thebone wire10 axially forward. Drilling through a sheath (not shown) helps protect surrounding tissue so that thethreads34 do not damage nearby soft tissue. Once thenarrower fragment section14 of thebone wire10 extends through thefragment30, thebone wire10 is no longer in threaded engagement with thefragment30. This leaves thecompression engagement36 to bias thefragment30 toward theanchor bone32. In the embodiment ofFIGS. 1-3, thecompression nut40 can be tightened with a wrench until thecompression shoulder38 engages the exterior surface of thefragment30 with the desired compression force. After the healing duration, thebone wire10 is simply removed from thebone20 by counterclockwise rotation of therotation section18, causing as little additional tissue damage as possible.

The present invention can be used on most types of fractures which have previously been treated by percutaneous pinning. Avulsion fractures of the hand and foot as well as reconstruction procedures such as IP fusions and hammertoe correction are excellent applications.

Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. In particular, the specific dimensions mentioned but not required by the claims are exemplary only, and do not limit the claimed invention.

Claims (25)

1. A bone fragment wire for connecting a bone fragment to an anchor bone for a healing duration and for extending out of the bone during the healing duration, the bone fragment wire comprising:

an elongated wire having a bone penetration section extending distally from a bone exterior section about a wire axis, the bone penetration section having a distal end and a proximal end with a bone penetration section length therebetween, the bone exterior section having a distal end and a proximal end with a bone exterior section length therebetween, the bone penetration section length being shorter than the bone exterior section length, the bone penetration section including a non-engaging fragment section and a bone anchor section located distally to the non-engaging fragment section, the non-engaging fragment section having a shaft with a shaft diameter of no greater than 0.1 inch, the bone anchor section having threads for engagement with the anchor bone, with a major diameter of the threads being greater than the shaft diameter of the non-engaging fragment section; and

a compression engagement on the bone exterior section, the compression engagement providing a shoulder which is longitudinally located at the distal end of the bone exterior section, the shoulder extending at a substantial angle to the wire axis for substantial contact with an exterior surface of the bone fragment; and

wherein the bone exterior section has external threads that mate with internal threads on the compression engagement, and wherein the inside diameter of the internal threads on the compression engagement is smaller than the shaft diameter of the non-engaging fragment section such that the internal threads on the compression engagement cannot advance onto the non-engaging fragment section.

2. The bone fragment wire ofclaim 1, wherein the bone exterior section has threads of a shallower pitch than the threads of the bone anchor section, and wherein the compression engagement is provided by a nut rotatably supported on the threads of the bone exterior section.

3. The bone fragment wire ofclaim 1, wherein the bone exterior section has threads of a different thread profile than the threads of the bone anchor section, and wherein the compression engagement is provided by a nut rotatably supported on the threads of the bone exterior section.

4. The bone fragment wire ofclaim 1, provided in a kit of a plurality of bone fragment wires each having a different length of non-engaging fragment section.

5. The bone fragment wire ofclaim 1, wherein the compression engagement has a proximal side with a sloped profile to assist in removing the compression engagement after a healing duration through tissue.

6. The bone fragment wire ofclaim 5, wherein a slope of the proximal side of the compression engagement increases from a gentle slope adjacent an outer diameter of the bone exterior section of the wire to a steeper slope distal to the gentle slope, thus providing a compression engagement of generally tear-drop cross-sectional shape.

7. The bone fragment wire ofclaim 1, wherein the compression engagement is permanently affixed to the wire.

8. The bone fragment wire ofclaim 1, wherein the shaft of the non-engaging fragment section is substantially smooth and cylindrical.

9. The bone fragment wire ofclaim 1, wherein the threads on the bone anchor section are self-tapping distally for insertion and self tapping proximally for removal.

10. The bone fragment wire ofclaim 1, wherein the compression engagement has a tear drop cross-sectional shape, wherein the compression engagement is permanently affixed to the wire, wherein the shaft of the non-engaging fragment section is substantially smooth and cylindrical, and wherein the threads on the bone anchor section are self-tapping distally for insertion and self-tapping proximally for removal.

11. The bone fragment wire ofclaim 1, wherein the shoulder of the compression engagement has a curvature to contact the exterior surface of the bone fragment along the curvature.

12. The bone fragment wire ofclaim 1, wherein the bone exterior section comprises:

a rotation section having a substantially smooth outer surface, and

a compression section extending distally from the rotation section, the compression section having external threads which mate with internal threads on the compression engagement, with the compression section being shorter than the rotation section.

13. The bone fragment wire ofclaim 1, wherein the non-engaging fragment section extends axially for 0.08 inch (2 mm) or more.

14. The bone fragment wire ofclaim 1, wherein the bone anchor section comprises a distal cutting tip for insertion into a bone without pre-drilling.

15. The bone fragment wire ofclaim 1, wherein a minor diameter of the threads on the bone anchor section is no less than the shaft diameter of the non-engaging fragment section, such that the bone anchor section overbores a hole for the non-engaging fragment section and the non-engaging fragment section does not interfere with bone threads left by advancement of the bone anchor section through a bone fragment.

16. A bone fragment wire for connecting a bone fragment to an anchor bone for a healing duration and for extending out of the bone during the healing duration, the bone fragment wire comprising:

an elongated wire having a bone penetration section extending distally from a bone exterior section about a wire axis, the bone penetration section having a distal end and a proximal end with a bone penetration section length therebetween, the bone exterior section having a distal end and a proximal end with a bone exterior section length therebetween, the bone penetration section including a non-engaging fragment section and a bone anchor section located distally to the non-engaging fragment section, the non-engaging fragment section being substantially smooth and cylindrical and having a shaft with a shaft diameter of no greater than 0.1 inch, the bone anchor section having threads for engagement with the anchor bone, with a major diameter of the threads being greater than the shaft diameter of the non-engaging fragment section; and

a compression engagement on the bone exterior section, the compression engagement providing a shoulder which is longitudinally located at the distal end of the bone exterior section, the shoulder extending at a substantial angle to the wire axis for substantial contact with an exterior surface of the bone fragment; and

wherein the bone exterior section has external threads that mate with internal threads on the compression engagement, and wherein the inside diameter of the internal threads on the compression engagement is smaller than the shaft diameter of the non-engaging fragment section such that the internal threads on the compression engagement cannot advance onto the non-engaging fragment section.

17. The bone fragment wire ofclaim 16, wherein a slope of the proximal side of the compression engagement increases from a gentle slope adjacent an outer diameter of the bone exterior section of the wire to a steeper slope distal to the gentle slope, such that the compression engagement has a generally tear drop cross-sectional shape.

18. The bone fragment wire ofclaim 16, wherein the compression engagement is permanently affixed to the wire.

19. The bone fragment wire ofclaim 16, wherein the threads on the bone anchor section are self-tapping distally for insertion and self tapping proximally for removal.

20. The bone fragment wire ofclaim 16, wherein the bone penetration section is shorter than the bone exterior section.

21. The bone fragment wire ofclaim 16, wherein the shaft diameter of the non-engaging fragment section is smaller than a minor diameter of the threads on the bone anchor section.

22. The bone fragment wire ofclaim 16, wherein the non-engaging fragment section extends axially for 0.08 inch (2 mm) or more.

23. A bone fragment wire for connecting a bone fragment to an anchor bone for a healing duration and for extending out of the bone during the healing duration, the bone fragment wire comprising:

an elongated wire comprising:

a bone exterior section, the bone exterior section comprising:

a rotation section having a substantially smooth outer surface, and

a compression section extending distally from the rotation section, the compression section having external threads; and

a bone penetration section extending distally from a bone exterior section about a wire axis, the bone penetration section comprising:

a non-engaging fragment section having a shaft with a shaft diameter, wherein the shaft of the non-engaging fragment section is substantially smooth and cylindrical; and

a bone anchor section located distally to the non-engaging fragment section, the bone anchor section having threads for engagement with the anchor bone, with a major diameter of the threads being greater than the shaft diameter of the non-engaging fragment section; and

a compression engagement providing a shoulder which is longitudinally located at a distal end of the bone exterior section, the shoulder extending at a substantial angle to the wire axis for substantial contact with an exterior surface of the bone fragment, the compression engagement having internal threads which mate with the external threads on the compression section, and wherein the inside diameter of the internal threads on the compression engagement is smaller than the shaft diameter of the non-engaging fragment section such that the internal threads on the compression engagement cannot advance onto the non-engaging fragment section.

24. The bone fragment wire ofclaim 23, wherein the non-engaging fragment section extends axially for 0.08 inch (2 mm) or more.

25. A bone fragment wire for connecting a bone fragment to an anchor bone for a healing duration and for extending out of the bone during the healing duration, the bone fragment wire comprising:

an elongated wire comprising:

a bone exterior section, the bone exterior section comprising:

a rotation section having a substantially smooth and cylindrical outer surface, and

a compression section extending distally from the rotation section, the compression section having external threads, the compression section being shorter than the rotation section; and

a bone penetration section extending distally from a bone exterior section about a wire axis, the bone penetration section comprising:

a non-engaging fragment section having a shaft diameter; and

a bone anchor section located distally to the non-engaging fragment section, the bone anchor section having threads for engagement with the anchor bone, with a major diameter of the threads being greater than the shaft diameter of the non-engaging fragment section; and

a compression engagement providing a shoulder which is longitudinally located at a distal end of the bone exterior section, the shoulder extending at a substantial angle to the wire axis for substantial contact with an exterior surface of the bone fragment, the compression engagement having internal threads which mate with the external threads on the compression section, and wherein the inside diameter of the internal threads on the compression engagement is smaller than the shaft diameter of the non-engaging fragment section such that the internal threads on the compression engagement cannot advance onto the non-engaging fragment section.

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